U.S. patent application number 10/220830 was filed with the patent office on 2003-08-28 for ventilated disk for disk brake.
Invention is credited to Tironi, Giovanni Mario.
Application Number | 20030159893 10/220830 |
Document ID | / |
Family ID | 8175230 |
Filed Date | 2003-08-28 |
United States Patent
Application |
20030159893 |
Kind Code |
A1 |
Tironi, Giovanni Mario |
August 28, 2003 |
Ventilated disk for disk brake
Abstract
Ventilated disc for a disc brake consisting of a friction track
(1, 2) and a disc hub (3) connected by means of pins (10) that are
partly embedded as inserts anchored irremovably in the material of
the track (1, 2) and partly inserted, in such a way that they can
freely slide axially, in the material of the disc hub (3), the said
friction track and disc hub being obtained in a single casting
process by using a common core with the pins held in the core.
Inventors: |
Tironi, Giovanni Mario;
(Bergamo, IT) |
Correspondence
Address: |
KENYON & KENYON
ONE BROADWAY
NEW YORK
NY
10004
US
|
Family ID: |
8175230 |
Appl. No.: |
10/220830 |
Filed: |
March 3, 2003 |
PCT Filed: |
February 12, 2001 |
PCT NO: |
PCT/EP01/01527 |
Current U.S.
Class: |
188/71.1 |
Current CPC
Class: |
F16D 2250/0007 20130101;
F16D 2065/138 20130101; B22D 11/0405 20130101; F16D 2065/1316
20130101; F16D 2065/1356 20130101; F16D 2065/1312 20130101; F16D
2065/1324 20130101; F16D 65/78 20130101; F16D 65/123 20130101; F16D
2065/134 20130101 |
Class at
Publication: |
188/71.1 |
International
Class: |
F16D 055/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 9, 2000 |
EP |
00830174.9 |
Claims
1. Ventilated disc for a disc brake, of the type in which a
friction track (1, 2) is produced by casting and connected to a
supporting disc hub (3), also cast, by means of connecting elements
in the form of pins (10) distributed around the perimeter of the
said supporting disc hub (3), the disc being characterized in that
the said pins have one end provided with gripping means firmly
embedded as an insert in the material of the said friction track,
and the opposite end housed as an axially sliding insert in the
material of the said disc hub.
2. Disc, according to claim 1, in which the said opposite end,
housed so as to slide freely in the disc hub, of the said pins is
lubricated with graphite.
3. Disc, according to claim 1 or 2, in which that end of each pin
which is embedded permanently in the friction track is provided
with grooves or reliefs for gripping purposes.
4. Process for producing a ventilated disc for a disc brake, with a
friction track (1, 2) and a disc hub (3) separated by an annular
space and connected to each other by a plurality of pins (10) with
one end engaged in the said track and the other in the said disc
hub, the said process comprising the following steps: forming a
casting core, in the general shape of a circular plate like the rim
of a hat, in which are inserted and positioned a plurality of pins
(10) oriented radially with respect to the centre (O) of the said
plate, their radially outer ends being provided with gripping
means, such as annular grooves, ridges or other similar reliefs and
depressions, and their radially inner ends being lubricated with
graphite, the said core having a thickened annular bead (25)
corresponding to the space between the said track and the said disc
hub for locating and supporting the said pins (10), placing the
said core (20, 21) in a mould (23, 24) configured in such a way as
to form, together with the said core, a first chamber (260)
corresponding to the said track and a second chamber (27)
corresponding to the said disc hub, in order to produce the said
track and the said disc hub together, attached by at least the said
pins, by casting in the said first and second chambers, pouring
molten metal into the said mould, demoulding the said friction
track and the said disc hub together, and removing unwanted metal
from the casting by machining it off.
5. Process, according to claim 4, in which the said thickened core
bead (25), together with the said casting, leaves at least one
connecting gap between the said first and second chambers so that
with a single casting of the same material, the said friction track
and the said disc hub are produced together, joined by the material
contained in the said gap as well as by the said pins.
6. Process, according to claim 5, in which the material
corresponding to the said gap is machined off.
7. Process, according to claim 4, in which the said core bead,
together with the said mould, completely separates the said first
cavity from the said second cavity so that materials having
differing mechanical characteristics can be cast into the two
cavities.
Description
DESCRIPTION
[0001] The present invention relates to a ventilated disc for a
disc brake and its method of manufacture.
[0002] More specifically, the present invention relates to a disc
for a disc brake for a vehicle.
[0003] It is known that in the brakes of vehicles, when the brakes
are applied, the kinetic energy of the moving vehicle is converted
into thermal energy or heat which builds up in the brake,
specifically in the disc of the brake, and must be dissipated in
order to prevent overheating which would prejudice its
efficiency.
[0004] For this purpose, brake discs have been developed in which
the friction track, on which the pads act, is made up of two
circular plates, rings, annuli or rims juxtaposed at a convenient
distance from each other and joined together by joining elements,
such as pegs, studs or flanges, in such a way as to form radial
channels for the circulation of air between the two rims and so
increase the radiating surface area of the disc and induce by
centrifugal action a much greater convective airflow than that
developed on the external surface of the disc, in the course of its
rotation, resulting in much more efficient cooling.
[0005] As is known, the two rims can be made separately and joined
together with bolts or rivets or even, preferably, they can be
produced as a single piece by casting.
[0006] Although this arrangement is very effective, the heating of
the rims cannot be limited sufficiently and produces large thermal
expansions in the rims relative to the radially more central part
of the disc.
[0007] Deformations of the disc therefore occur: these prejudice
braking efficiency, can lead to disc breakage due to thermal
fatigue and must at all costs be prevented.
[0008] To this end the usually bell-shaped central part of the disc
or disc hub, whose function is to provide support and anchorage to
the wheel hub, is in many cases produced separately from the
friction track and joined to it by constraints that transmit
rotational drive to the friction track and transfer a torque to the
disc hub and, at the same time, allow freedom of radial movement to
permit thermal expansion of the friction track without the
development of internal tensions in the disc hub.
[0009] The constraints also limit the transfer of heat, by
conduction, from the friction track to the disc hub and to the
wheel hub.
[0010] The result of this is a highly complicated structure of not
insignificant cost, to simplify which it has been proposed, as
described for example in document EP 0,680,571, that the friction
track be cast, with radial housings being drilled in the friction
track, and the disc hub being attached to the friction track by
pins integral with the disc hub and inserted, with the ability to
slide freely axially, in the housings formed in the friction track,
thus permitting thermal expansion of the friction track.
[0011] The pins may be fastened to the disc hub by welding or by
embedding one end thereof as an insert in the molten metal of the
disc hub.
[0012] This presupposes the prior formation of the friction track,
the insertion of the pins into the housings of the friction track,
the formation of a mould for the disc hub, in which to at least
partly place the already-prepared friction track, or at least the
ends of the pins, and the subsequent casting of the disc hub.
[0013] Although the production process is to a certain degree
simplified, it is still complicated and expensive owing to the
necessity of machining the housings for the pins and to the
construction of independent moulds for the friction track and for
the disc hub, as well as to the performing of successive
castings.
[0014] Moreover the locking of the pins as inserts in the disc hub,
the thickness and general dimensions of which ought to be limited,
is not reliable.
[0015] The final drawback is that the finishing of the disc hub and
the balancing of the assembled disc are problematic operations.
[0016] All these problems are solved by the ventilated disc for a
disc brake and its method of manufacture forming the subject of the
present invention.
[0017] According to this invention the brake disc consists of a
cast friction track or rim to which a disc hub, which is produced
in the same casting process (with a single mould although not
necessarily with the same cast material), is attached by means of
partly embedded pins integral with the track and partly embedded,
but with freedom of axial movement, in the disc hub in such a way
as to permit, under working conditions, thermal expansion of the
rim around the disc hub and at the same time ensure a precise
permanent mutual coupling, without play, between rim and disc hub.
By this means the operations of mechanically finishing and
balancing the disc are enormously simplified and made very
simple.
[0018] The features and advantages of the invention will become
clearer in the course of the following description of a preferred
embodiment and of variants thereof. The description refers to the
appended drawings in which:
[0019] FIG. 1 is a front view, partly in section as indicated by
the view marked I-I in FIG. 2, of a ventilated disc in accordance
with the present invention,
[0020] FIG. 2 is a diametrical view through the disc seen in FIG. 1
along the composite section marked II-II in FIG. 1,
[0021] FIG. 3 illustrates a sector of a core, viewed as indicated
by the composite section III-III in FIG. 4, used for casting the
ventilated disc seen in FIGS. 1 and 2,
[0022] FIG. 4 is a section through the sector of the core viewed on
IV-IV as marked in FIG. 3 and of the mould used for producing the
disc seen in FIGS. 1 and 2,
[0023] FIG. 5 is a section on the view marked IV-IV in FIG. 3
through the casting obtained with the mould and associated core of
FIG. 4,
[0024] FIG. 6 is a section taken on the view marked IV-IV in FIG. 3
through the brake disc produced with mechanical finishing of the
casting seen in FIG. 5, and
[0025] FIG. 7 is a section taken on the view marked IV-IV in FIG. 3
through a variant of the casting.
[0026] Referring to FIGS. 1 and 2 together, a brake disc in
accordance with the present invention comprises a friction track or
rim made up of two flat rings or plates 1, 2 and a mounting element
or disc hub 3. Both are made by casting.
[0027] The rings 1, 2, which are axially aligned, parallel with
each other and set a suitable distance apart, are interconnected by
a plurality of bridges, such as 4, 5, 6, suitably shaped to create,
between the rings, a series of generally radial aeration ducts
through which the air can flow, largely unimpeded, from the inner
edge 7 of the friction track towards the peripheral outer edge
8.
[0028] Embedded in each of a suitable number of bridges 4 that meet
the inner edge 7 of the said friction track, in a uniform
distribution, is one end of a corresponding number of cylindrical
pins, such as 10, arranged like spokes.
[0029] The embedded end of each pin 10 has annular grooves (or
equivalent variations of thickness such as ridges, indentations and
the like) so that the pins are held rigidly as inserts in the cast
material of the rings 1, 2 and of the bridges 4, 5, 6.
[0030] The pins may advantageously be made from a tough,
high-strength material such as stainless steel or carbon steel,
while the material of the rings, for which great hardness and
resistance to abrasion are required, is generally cast iron.
[0031] The pins 10 provide the connection with the supporting disc
hub 3.
[0032] The disc hub consists of a cylindrical body, slightly
conical for ease of demoulding, partly closed at one end by a flat
rim 11 containing holes at suitable points for fixing to a wheel
hub, and terminating at the other end in a thickened flange whose
periphery is close to the inner edge 7 of the friction track, from
which it is separated by a suitable distance or space D of the
order of a few millimetres.
[0033] The flange of the disc hub 3 is similarly formed from two
axially aligned rings 12, 13 parallel with each other and a
suitable distance apart: they are connected by a plurality of
bridges, such as 14, shaped to form, between the rings, a series of
radial aeration ducts 15 through which the air can flow
unobstructed towards the innermost channels of the friction track
1, 2.
[0034] The other ends of the pins 10 are inserted into each of a
suitable number of bridges 14 through which they pass completely
and in which they can slide axially.
[0035] Together, the pins provide an accurate and precisely centred
coupling between the friction track and the disc hub 3 and at the
same time allow the track to expand thermally relative to the disc
hub.
[0036] The result is a brake disc of the greatest constructional
simplicity and of great reliability, in which excellent ventilation
is provided by broad channels that enable a flow of air to enter
between the rings 1, 2 both from the centre of the disc hub 3
(flowline 16) and from the sides of the rings 12, 13 (flowlines 17,
18).
[0037] As will be seen later, the material of the disc hub 3 may be
the same as that used for the friction track, e.g. cast iron, or
may be a material with different mechanical characteristics, e.g.
steel or a light alloy.
[0038] To manufacture the disc described above, the following
process is employed:
[0039] A casting core is first formed in moulding sand, or
preferably in core sand, in the general shape of a circular plate
like the rim of a hat 20, with the central portion like a
cylindrical cup 21 of axis O.
[0040] One sector of the core is shown in plan view in the section,
FIG. 3, and a view in diametrical cross section through the same
sector is shown in FIG. 4.
[0041] The solid part of the hat rim 20 corresponds, of course, to
the open parts that must be left in the interior of the friction
track and of the flange of the disc hub, while the central cupped
portion 21 acts as a complementary mould or cope.
[0042] The edge of the plate is reinforced by a thick core print or
rim 22 standing proud of the plate both below and above to act as a
spacer for the mould or drag, shown schematically in FIG. 4 by the
broken line 23, and for the cope, shown diagrammatically in FIG. 4
by the broken line 24. In other words the said core print holds and
supports the core in the correct position for casting.
[0043] A second circular bead 25 stands proud both below and above,
in an intermediate position on the hat rim 20 close to the central
cup 21, its purpose being to form the annular separating space
(space D, FIG. 1) between friction track and disc hub.
[0044] The voids 4, 5, 6 of the core correspond to the bridges with
the same reference numbers (in FIG. 1) that connect together the
two rings of the friction track.
[0045] Void 14 of the core sector, and the other similar voids (not
shown), correspond to the bridges 14 (FIG. 1) that connect together
the two rings of the disc hub flange.
[0046] The pins such as 10 designed to couple the friction track
and the disc hub are housed and positioned accurately in the
core.
[0047] Accurate and stable positioning, even in the presence of
stresses induced by the fluid mass as it is poured in, is ensured
by the core print or rim 22, as well as by the bead 25 and by the
cylindrical portion of the cup 21.
[0048] Clearly, the core box in which the core is formed includes
filled areas, corresponding to the core voids 4 and 14, containing
housings for the precise reception of the pins 10 which are thus
partly incorporated in the core.
[0049] The portion of each pin 10 lying in the voids such as 4 is
provided with annular grooves 26 whose purpose is to securely fix
the grooved portion to the material of the casting.
[0050] The other portion of each pin 10 is advantageously
lubricated with graphite so that it does not become welded to the
molten metal during the subsequent casting.
[0051] The core formed in this way is located (FIG. 4) in a drag
23, which is essentially a flat disc with a suitable frustoconical
recess in the centre, with the cup of the core housed in the recess
and resting on its bottom and the rim 22 resting on the surface of
the disc.
[0052] The drag is closed by a cope 24, which is also a flat disc,
with a frustoconical relief that fits into the cavity of the cup of
the core, on which it rests.
[0053] The flat disc however rests on the rim 22 and on the bead
25.
[0054] The cope is of course provided with sprue holes and vent
holes (not shown), as may also the drag, depending on the methods
and positioning of the mould for the casting. For example, it may
be convenient to cast with the mould upside down compared with FIG.
4, and in particular with the cope 24 underneath the drag 23 so
that as the molten metal is poured into them it initially fills
chambers 260 and 27 if these are connected to each other.
[0055] It will be observed that the bead 25 does not rest on the
drag 23 and that the void left between the drag and the cope
consists essentially of two separate chambers 260, 27 communicating
with each other through a gap 30 left between the bead 25 and the
drag 23.
[0056] As a variant, another gap may also be left between the bead
25 and the cope 24.
[0057] In this way in a single casting operation the two
communicating chambers 260, 27 can be filled with molten metal of
the same type, such as cast iron.
[0058] After the metal has been cast and allowed to cool, the
casting can be extracted from the mould and the core removed by
shaking and optionally by blasting.
[0059] The resulting product is illustrated in cross section in
FIG. 5.
[0060] It will be seen that the friction track 28 and the disc hub
29 are joined together by means of the pins 10 and by the material
filling the gap 30 (and an optional gap 31, if provided as in the
variant).
[0061] In addition, the pins 10 project somewhat into the disc hub
29 because their ends were conveniently inserted in the material of
the core for more secure and precise positioning.
[0062] At this point it is possible, by lathe-turning operations
(quite easy because the workpiece is monolithic and the various
clamping and reference points can be determined accurately at each
stage of the operation), to remove all the excess unwanted metal
from the intended final product, particularly the projecting parts
of the pins 10 and the unwanted metal 32, 33 of the disc hub
flange, including the material occupying the gap 30 and the
optional gap 31.
[0063] Holes 34 are also made (or bored out if already present in
the casting) in the disc hub (FIG. 6) so that it can be fixed to a
wheel hub, and finally the disc is balanced.
[0064] The resulting product is shown in section in FIG. 6.
[0065] Mention has been made in the course of the above description
of possible alternative embodiments of the core (two gaps 30, 31
instead of only one, disc hub holes produced by the core during
casting) which lead to the formation of castings which are
different in certain details but which lead, after machining, to
the same finished product.
[0066] A further variant which it is worth mentioning specifically,
is the following: the core of FIG. 4 and/or the corresponding drag
and cope can be produced in such a way that the bead 25 completely
separates the chamber 260, representing the friction track, from
the chamber 27, representing the disc hub.
[0067] By this means, and of course providing separate pouring and
vent holes, it is possible to obtain by casting, preferably in
casting operations following immediately one after the other, if
not simultaneous, both the friction track and the disc hub from
different materials, for example cast iron and steel, with
differing mechanical characteristics specifically suited to the
particular function the two components are to perform. In this
case, as shown in the sectional view of FIG. 7, the two components
of the casting are attached to each other mechanically by the pins
10 only.
* * * * *